This time of year there is very little good diving off Kaua'i.  However,
there is some excellent hiking along the Na Pali coast.  So bring your dive
gear, but don't expect the world, but also bring you hiking boots and expect
so fantastic views.  And while you are driving toward the Na Pali coast for
your hike, look out at the Island of Ni'ihau, the "Forbidden Isle."  That's
where the real diving is.  You just can't get there this time of year.
http://www.bubblesbelowkauai.com/niihau.html

Note:  I do not endorse "Bubbles Below."  I' have always found the crew to
be great but the owner to be not so great.

I forgot to include this:
http://www.shorediving.com/Earth/Hawaii/Kauai/index.htm

And this: http://www.hawaii.gov/dlnr/dsp/NaPali/na_pali.htm